1. Field of the Invention
The present invention relates to a carriage driving unit for reciprocating a carriage mounted with a recording head or the like via a timing belt driven by a motor, and to an image recording apparatus utilizing the carriage driving unit.
2. Description of Related Art
In a conventional image recording apparatus, since easy to manufacture, there has been used a toothed driving pulley 100 formed with a flange 104 only at a side opposite to a flat surface 102 as shown in FIG. 1 (Japanese Patent Application Laid-Open No. 2005-246907). The toothed driving pulley 100 is attached to a driving shaft of a drive motor 108 attached to a guide member 106. And a timing belt 110 is laid around between the toothed driving pulley 100 and a driven pulley (not shown).
However, when the toothed driving pulley 100, which is formed with the flange 104 only at one side, is driven to rotate by the drive motor 108, the timing belt 110 occasionally moves toward the flat surface 102 where the flange 104 is not formed as indicated with double-dotted lines in FIG. 1. On the flat surface 102, there are various protruding items, for example, catches 114 for connecting the guide member 106 and a frame body 112, fixing portions 116 used for inserting to attach a holder for rotatably supporting spurs (not shown) to the guide member 106 and the like.
In order to prevent the timing belt 110 from coming into contact with these projections and getting damaged even when the timing belt 110 moves toward the flat surface 102 indicated with the double dotted lines in FIG. 1, a sufficient space is ensured between the timing belt 110 and the projections. Therefore, there resides such a disadvantage that the height of the toothed driving pulley 100 and the timing belt 110 from the flat surface 102 become considerably high resulting in a increase of size of the carriage driving unit.